American Marten Recovery in the Northeast

Over-harvesting and habitat loss in the northeastern United States has caused steep declines in populations of the American marten. The American marten is an important species, considered an indicator of forest health and snow pack, and serves as an umbrella species, supporting habitat conditions for many other species. States in the northeast are prioritizing marten recovery, especially New Hampshire and Vermont where the marten is threatened and endangered, respectively.

Not much is known on the current distribution of marten and how landscape characteristics shape occupancy patterns in the region. Marten have not been comprehensively surveyed in the northeast and localized trapping may not be enough to provide distribution information. This lack of information is problematic, because it impedes development of effective recovery strategies and regional conservation planning.

Researchers from the Wildlife and Fisheries Biology Program at the University of Vermont and the Vermont Cooperative Fish and Wildlife Research Unit, in partnership with the Vermont Department of Fish and Wildlife, surveyed experts on the occupancy of American marten to estimate distribution and connectivity in the northeast to aid in marten recovery efforts.

A survey gathered opinions from eighteen experts to build a model describing marten occupancy in the northeast. Experts included researchers, trappers and wildlife managers. Each expert estimated the probability of occupancy at about 30 sites within their region of expertise.

Models estimating landscape quality were derived from the survey results and the best fitting model indicated that five landscape characteristics describe occupancy: percent canopy cover, percent spruce-fir landscape cover, winter temperature, elevation, and road density. Modeling showed that preserving unfragmented, old growth, high-quality habitat areas will be crucial for marten recovery in the northeast. Limiting road development and other practices that create lower quality edge habitats will help maintain these higher quality habitat areas.

Climate change will also affect marten recovery. Models from the study showed that higher elevations and lower temperatures (indicators of greater snow pack) help with marten occupancy. However, climate change is predicted to increase temperatures and reduce snow pack in the northeast. Better understanding how climate change could affect martens and how they might adapt to different habitat conditions will facilitate recovery and resilience in marten populations. The model was also used to identify areas of high quality habitat between populations that could be used for movement. Enhancing gene flow between populations could increase their resilience to local population declines.  

Tests of model performance showed that the data from experts were effective at modeling patterns of marten occupancy and researchers believe the results will provide useful information for future marten recovery planning in the northeast. This study also illustrates that expert opinion data can provide an effective means of describing the distribution of rare, elusive, and difficult-to-detect species.

Distribution and connectivity maps developed by the project are available for download on the Forest Ecosystem Monitoring Cooperative website: https://www.uvm.edu/femc/data/archive/project/marten.